1. Technical Field
The present invention relates to an oscillator.
2. Related Art
Micro-electromechanical systems (MEMS) are one of microstructure formation technologies, and denote, for example, a technology of manufacturing a micron order of fine electronic machine system and products derived therefrom. A vibration element (a MEMS vibrator) made using the MEMS technology has been developed. Further, an oscillator using the MEMS vibrator has been developed.
One of the important characteristics of the oscillator is frequency accuracy. However, there is a limitation in raising the working accuracy in production of the MEMS vibrator itself in order to obtain high frequency accuracy. Therefore, there has been known a method of performing trimming on the MEMS vibrator itself to thereby fine-tune the frequency in order to obtain high frequency accuracy.
Further, JP-A-2010-56764 discloses the MEMS vibrator the resonant frequency of which can be controlled in accordance with a controlling direct-current voltage supplied externally.
However, in order for performing trimming on the MEMS vibrator itself, a working machine dedicated to trimming and the time for performing trimming become necessary. Therefore, it is disadvantageous in terms of manufacturing cost. Further, since there is no chance to perform trimming after the MEMS vibrator is encapsulated in a package, it is difficult to perform accurate trimming considering the influence of the parasitic component of the package.
Further, in the MEMS vibrator disclosed in the patent literature described above, since it is required to continue to externally provide the controlling direct-current voltage with an appropriate value, the device is difficult to use as an oscillator.